Medical Expert Systems

Eddie Lai

History 1950s – scientists tried to use computers for

“probabilistic reasoning and statistical pattern recognition”

1970s – realized that physicians do not make decisions based on probability or patterns

Several expert systems a.k.a knowledge based systems were released shortly after MYCIN ONCOCIN

MYCIN Expert system to identify bacteria that was

causing infections and then prescribe antibiotics

Developed in early 1970s Written in LISP Only used as research, never in practice Found that MYCIN gave acceptable

conclusions more often than disease experts Beginning of expert systems; many other

expert systems were released after this

What is ONCOCIN? Medical expert system written in LISP Developed in Stanford’s School of Medicine in

1979 Intended for use by oncologists Used at Stanford’s Oncology Clinic Used for managing patients already diagnosed

with cancer and being treated with chemotherapy Alter/delay treatment based on condition after

certain treatment Thousands of possibilities given the side effects of

chemotherapy

ONCOCIN Composed of two systems

Reasoner – knowledge base and logic Interviewer – interface between ONCOCIN and

user (oncologist) Each runs on parallel processors to not slow

each other User enters information about patient (rather

than what he used to do) Reasoner returns conclusions for current visit

and recommendations for next visit User can choose what to pass on to patient

Knowledge Base Representation Contexts

Organizing the knowledge base:“disease”, “protocol”, “chemotherapy”

Protocol – set of treatments to treat a certain tumor Parameters

Patient attributes: blood cell count, test results, etc. Used to determine next step

Rules Data driven (forward chaining) or goal-driven (backward

chaining) Recommendations on dosages

Control blocks Steps of performing treatment, dosages. Calculating dosage

Sample rules

Heirarchy

Inputting data Lots of information about cancer and

treatments released constantly Too much to frequently release new systems Solution: must allow oncologists to input data OPAL – graphical program used to add/modify

a chemotherapy protocol Add new flow chart Create tree to follow a treatment

References http://www.ncbi.nlm.nih.gov/pmc/articles/PMC

1307157/?page=1Medical Expert Systems—Knowledge Tools for

Physicians by Edward H. Shortliffe, MD, PhD http://citeseerx.ist.psu.edu/viewdoc/summary?

doi=10.1.1.80.5446ONCOCIN: AN EXPERT SYSTEM FOR ONCOLOGY

PROTOCOL MANAGEMENT Edward H. Shortliffe, A. Carlisle Scott, Miriam B. Bischoff, A. Bruce Campbell, William Van Melle,

http://en.wikipedia.org/wiki/Mycin

Questions?